I installed two sets of sights this week (XD and G17.5) and both rears needed quite a bit of stoning to fit. The G17.5 was getting a replacement Night Fision sight and they must have sent him a factory defect to replace the one that had a burned out lamp. It was visibly bowed and had to be fitted more than any other Glock sight I've installed.
I use this one . I've pushed them on and off both ways. Never had a problem. If you ram a tight sight in one way, then force it straight through the other side later it can supposedly open up the dovetail too much for future sights. Sounds plausible.